Radiation in a hypersonic shock layer generated around a projectile

Radiation emitted from the shock layer generated around a hypersonic flight model is experimentally investigated by using a ballistic range (two-stage light-gas gun). A polyethylene projectile of 1.2 cm in diameter is launched in this facility at the velocity of 5 km/sec (M=15), and the emission from the induced shock layer around the projectile is observed with a spectroscope. As a result, molecular band-spectra from NO and N₂ are detected along with those from carboncontaining molecules. Total emission power is measured with a diode-type powermeter. In addition, dimension effect of the flight model is theoretically and numerically examined, and a scaling law on thermochemical structure of the shock layer is developed. It shows that the thickness of thermal boundary-layer formed on the model surface does not follow the conventional scaling law based on the reaction distance and on the energy relaxation distance. Finally, the radiative field around the projectile is numerically computed, and the total power emitted from the shock layer is estimated. From the comparison between computed and measured results, the validity of the calculation model is discussed.     

Radiation effects on dihydroxypropyl-chitosan

Dihydroxypropyl-chitosan (DHP-chitosan), a derivative of chitosan used in practical applications, is hardly soluble in water because of the strong intermolecular hydrogen bonding. In order to improve its even more advanced practical applications, some further modifications of the polymer using electron beam radiation technique were carried out. In the current work, diluted lactic acid was used to improve the solubility of DHP-chitosan as a subversive of hydrogen bonding. The effects of electron beam radiation on the DHP-chitosan in solid state and solution state were investigated. It was found that solid state and low concentrated solution state result in degradation and high concentrated solution state is favorable for crosslinking. And a simple, effective strategy to achieve a novel DHP-chitosan hydrogel without any crosslinking agents was developed in a high concentrated polymer solution system under irradiation.     

Heat transfer in MHD viscoelastic fluid flow over a stretching sheet with variable thermal conductivity,non-uniform heat source and radiation

An analysis has been carried out to study the magnetohydrodynamic boundary layer flow and heat transfer characteristics of a non-Newtonian viscoelastic fluid over a flat sheet with a linear velocity in the presence of thermal radiation and non-uniform heat source. The thermal conductivity is assumed to vary as a linear function of temperature. The basic equations governing the flow and heat transfer are in the form of partial differential equations, the same have been reduced to a set of non-linear ordinary differential equations by applying suitable similarity transformation. The transformed equations are solved analytically by regular perturbation method. Numerical solution of the problem is also obtained by the efficient shooting method, which agrees well with the analytical solution. The effects of various physical parameters such as viscoelastic parameter, Chandrasekhar number, Prandtl number, variable thermal conductivity parameter, Eckert number, thermal radiation parameter and non-uniform heat source/sink parameters which determine the temperature profiles are shown in several plots and the heat transfer coefficient is tabulated for a range of values of said parameters. Some important findings reported in this work reveals that combined effect of variable thermal conductivity, radiation and non-uniform heat source have significant impact in controlling the rate of heat transfer in the boundary layer region.     

A novel far-boundary condition for the finite element analysis of infinite reservoir

The present paper deals with the finite element analysis of the reservoir of infinite extent using a novel far-boundary condition. The equations of motion are expressed in terms of the pressure only assuming water as inviscid and incompressible. The truncation boundary condition is developed numerically from the classical wave equation. Comparative studies show that the proposed far-boundary condition is numerically efficient and accurate over the existing ones, available in the literature. The effect of the geometry of the reservoir bed and the adjacent structure on the development hydrodynamic pressure has been studied. The results show that the geometry of the reservoir bed and as well as the adjacent structure has considerable effect on the development of hydrodynamic pressure at the dam–reservoir interface.     

Development of an X-ray detector using surface plasmon resonance

A new X-ray detector using surface plasmon resonance (SPR) is proposed. The detector consists of a prism coated with a thin metal film and semiconductor film. Optical laser pulse induces SPR condition on the metal surface, and synchronized X-ray pulse which is absorbed into the semiconductor film can be detected by measuring the change of the resonance condition of the surface plasmon. The expected time and spatial resolution of this detector is better than that of conventional X-ray detectors by combining this SPR measurement with ultra-short laser pulse as the probe beam. Our preliminary investigation using Au and ZnSe coated prism implies this scheme works well as the detector for the ultra-short X-ray pulse.     

中医方药量化研究中“相对药量”的数学模型体系

建立中医方药量华研究的"相对药量"概念模型体系;方法:运用微分方程理论;提出五种情况下,中药常用量范围内相对药量概念的数学模型,分别为直线模型、指数函数模型、对数函数模型、二次函数模型(开口向上和向下两种),并说明该模型体系的和理性与适应性;结论:相对药量概念核心体系的建立,增加了中医方药"相对药量"可比性的全面性,这对进一步研究单位药乃至方剂中各药在性、味、归经等方面的影响程度及其规律性,将起到至关重要的作用.     

Escape factors in zero-dimensional radiation-transfer codes

Several zero-dimensional non-LTE radiation-transfer codes are in common use within the laser-plasma community (for example, RATION, FLY, FLYCHK and GALAXY). These codes are capable of generating calculated emission spectra for a plasma of given density and temperature in the presence of a radiation field. Although dimensionless in nature, these codes can take into account the coupling of radiation and populations by use of the escape factor method, and in this sense the codes incorporate the finite size of the plasma of interest in two ways – firstly in the calculation of the effect of the radiation on the populations and secondly when using these populations to generate a spectrum. Different lengths can be used within these two distinct operations, though it has not been made clear what these lengths should be. We submit that the appropriate length to use for the calculation of populations in such zero-dimensional codes is the mean chord of the system, whilst when calculating the spectrum the appropriate length is the size of the plasma along the line of sight. Indeed, for specific plasma shapes using the appropriate escape factors it can be shown that this interpretation agrees with analytic results. However, this is only the case if the correct escape factor is employed: use of the Holstein escape factor (which is in widely distributed versions of the codes mentioned above) is found to be significantly in error under most conditions. We also note that for the case where a plasma is close to coronal equilibrium, some limited information concerning the shape of the plasma can be extracted merely from the ratio of optically thick to optically thin lines, without the need for any explicit spatial resolution.     

Interaction of shock waves during the passage of a disrupted meteoroid through the atmosphere

The motion of fragments following disintegration of a meteoroid during its flight through the Earth's atmosphere is investiated. Shock wave configurations, aerodynamical forces and moments acting on each fragment and the trajectories of the pieces are determined for hypothetical initial configurations. The results of numerical simulations show that a meteoroid's breakup may lead to both increase and decrease of the total cross section, drag forces and energy release in the atmosphere. As a consequence the emitted radiation varies.